1. Field of the Disclosure
The present disclosure relates to an interlock apparatus of a ring main unit, and particularly, to an interlock apparatus of a ring main unit, which enables a state of a disconnector to be controlled based on a state of a circuit breaker included in the ring main unit.
2. Background of the Disclosure
Generally, a ring main unit is an apparatus that is used for monitoring, controlling, and protecting an electric system used to receive and distribute power supplied from power distribution equipment. The ring main unit is configured with an array where a circuit breaker, a switchgear, a ground, conductors, and the like are included in a structure sealed and insulated by an SF6 gas.
The ring main unit includes a circuit breaker, a load switch, a fuse, a disconnector, etc. A cable cover is detachably attached on the ring main unit, for protecting each of circuits.
FIG. 1 is a front view illustrating a state where a cover is removed from a related art ring main unit 10. FIG. 2 is a perspective view illustrating a circuit breaker included in the related art ring main unit 10. FIG. 3 is a perspective view illustrating a disconnector included in the related art ring main unit 10. FIG. 4 is a front view illustrating the disconnector included in the related art ring main unit 10. FIG. 5 is a perspective view illustrating a handle for controlling a state of the disconnector included in the related art ring main unit 10. FIG. 6 is a perspective view illustrating a state where the handle is caught in the disconnector included in the related art ring main unit 10.
As illustrated in FIGS. 1 to 5, the related art ring main unit 10 includes a circuit breaker 11, a disconnector 13, and a load switch (not shown). An interlock apparatus is provided between the circuit breaker 11 and a cable cover (not shown). Also, the interlock apparatus is provided between the disconnector 13 and the cable cover. Therefore, the cable cover may be detached only when the circuit breaker 11 and the disconnector 13 are in a cutoff state.
At this time, an open/closed state of the circuit breaker 11 is controlled through a button, and an open/closed state of the disconnector 13 is controlled by rotating a handle 20 by about 180 degrees after the handle 20 is inserted into an insertion hole 13a provided in the disconnector 13.
However, in the related art ring main unit 10, the interlock apparatus is not provided between the circuit breaker 11 and the disconnector 13, and for this reason, even when the circuit breaker 11 is in a closed state, a state of the disconnector 13 is controlled by rotating the handle 20 after the handle is inserted into the insertion hole 13a. 
Moreover, if the disconnector 13 having no load switching function operates when the circuit breaker 11 is in the closed state, a large shock is applied to the ring main unit 10, and for this reason, the ring main unit 10 is largely broken.
Moreover, if the disconnector 13 operates when the circuit breaker 11 is in the closed state, a negligent accident occurs in use, and for this reason, the risk of life loss is large.